The ink jet method of printing is a rapidly growing, commercially important printing process because of its ability to produce economical, high quality, multi-colored prints. Ink jet printing is becoming the method of choice for producing colored hard copy of computer generated images consisting of graphics and fonts in both narrow and wide format.
Current ink jet printing technology involves forcing ink drops through small nozzles by piezoelectric pressure, thermal ejection, or oscillation onto the surface of a material. An aqueous ink of low viscosity consisting of direct dyes or acid dyes is commonly used in ink jet printing. More specifically, the ink used in ink jet printing typically consists of an aqueous solution of dye, a humectant, and a pH buffer. These formulations are desirable because of their low cost, availability, safety, and environmental friendliness. In ink jet printing, uniformly shaped droplets of the aqueous formulation are ejected from a nozzle as very small drops onto a printing material. The printing material should allow for printing of round, well-shaped dots of high optical density. The material should control feathering (spreading) of the ink drops and absorb the ink vehicle rapidly (fast dry time) while adsorbing the dye at the surface to give sharp high density prints.
Ink jet printing of textiles is a relatively new technology that is gaining acceptance in the textile community. There are, however, several technical challenges associated with such ink jet printing. As noted above, ink jet printing almost universally requires the use of aqueous inks based on water-soluble dyes. Consequently, these dye-based inks are transparent. When an ink jet ink is printed on a textile which already has been dyed with a color darker than the color of the ink jet ink to be printed, the ink jet ink either cannot be detected visually or is too faint. Moreover, the underlying color of the textile, even if it is not darker than the ink jet ink to be printed, often alters the perceived hue of the printed ink jet ink. If the textile were selectively decolorized, the ink jet ink could be printed on the decolorized areas, thereby avoiding the problems just described. Although ink compositions based on nonaqueous systems are being developed for use in ink jet printing of textiles, such compositions are not known to be widely used; see, by way of example only, European Patent Specificaton Nos. EP 0 757 731 B1 and EP 0 778 907 B1 to Videojet Systems International, Inc.
The decolorization of dyed textiles is, of course, well known. By way of example, the enzymatic discharge printing of dyed textiles is described in Published International Application WO 98/46820 to Novo Nordisk Biochem North America, Inc. [see, also, Published International Applications WO 96/12845 and WO 96/12846 to Novo Nordisk A/S, both of which relate to enzymatic bleaching processes; Published International Application WO 96/10079 to Novo Nordisk A/S, which relates to enhancing agents, detergent additives, and detergent compositions; Published International Application WO 98/05816 to Novo Nordisk Biochem North America, Inc., which relates to an enzymatic method for overdying cellulosic textiles; and the Japanese article published in Shizuoka-ken Hamamatsu Kogyo Gijutsu Senta Kenkyu Hokoku (1997), 7, 21-26]. In the disclosed method, a dyed fabric is contacted with a phenol oxidizing system and an enhancing agent to selectively discharge dye from the fabric at selected areas. The phenol oxidizing enzyme is selected from the group consisting of peroxidase, laccase, catechol oxidase, bilirubin oxidase, and monophenol monooxygenase. The enzyme and enhancing agent may be applied to the fabric concurrently or separately in any order.
In the examples, discharge images were produced on dyed fabric by means of a manual screen printing method. A suitable silk screen design was prepared and the screen was placed on top of the fabric. A paste of the phenol oxidizing enzyme (laccase) and the enhancing agent (10-phenothiazine-propionic acid) was forced through the silk screen design onto an adjacent piece of fabric, resulting in the transfer to the fabric of the pattern of the screen.
While not directly related to the above method, U.S. Pat. No. 5,480,801 to Wahleithner et al.; U.S. Pat. No. 5,770,419 to Feng et al.; and Published International Applications WO 98/27197 and WO/9827198 to Novo Nordisk A/S are of interest as they relate to various laccases.
Enzymes also have been used to remove excess dye from textiles. See, by way of illustration only, European Patent Specification EP 0 580 707 B1 to Novo Nordisk A/S. According to the reference, it has been found possible to decolorize dye leached from dyed or printed textiles in an aqueous solution by adding enzymes utilizing hydrogen peroxide or molecular oxygen for the oxidation of organic or inorganic substances, including colored substances, together with a source of hydrogen peroxide or oxygen.
Several processes are described including a process for simultaneous bleaching of dye and formation of localized color variation in fabrics or garments made from differently colored materials; a process for inhibiting backstaining of denim garments during finishing; and a process for simultaneous removal of excess dye and removal of starch from newly manufactured printed or dyed fabric or yarn. Enzymes suitable for such processes are oxidases and peroxidases, collectively referred to as bleaching enzymes. Examples of such enzymes include catechol oxidase, laccase, peroxidase, chloride peroxidase, and phenol oxidase. It therefore can be seen that there is still a need in the art for a method for decolorizing a material in a predetermined pattern.